1. Field of the Invention
The present invention relates to a gas insulated switchgear, and more particularly to a gas insulated switchgear having a trapping unit that traps metal foreign matters.
2. Description of the Related Art
A gas insulated switchgear is configured such that various devices such as a breaker, bus lines, a disconnector, and a current transformer for instruments are accommodated in a tank enclosing insulation gas such as SF6 (sulfur hexafluoride) gas.
Meanwhile, metal foreign matters are mixed in the content of a tank of a gas insulated switchgear in some cases. The metal foreign matters are moved by an electric field in the tank, and this can be a cause for deteriorating the insulation performance of the switchgear. Therefore, it is desired to eliminate or trap the metal foreign matters.
For example, Japanese Patent Application Laid-open No. H07-245853 discloses a gas insulated electrical device, in which a groove is formed in an inner peripheral surface of a flange that mounts an insulation spacer. Because the groove forms a low electric field portion, metal foreign matters fall into the groove and thus these matters are rendered harmless.
However, because the conventional technique of Japanese Patent Application Laid-open No. H07-245853 requires performing a groove machining on a flange, which is a portion of a tank, the cost increases.